The invention relates to an optical storage apparatus using a removable medium such as magnetooptical cartridge, phase-change type optical disk, DVD-RAM, or the like and, more particularly, to an optical storage apparatus for executing an access of a command while deciding an optimum light emitting power by a test writing on a medium when receiving a host command.
An optical disk has been highlighted as a storage medium serving as a core of multimedia which has rapidly been developed in recent years. For example, in case of an MO cartridge of 3.5 inches, in addition to conventional medium of 128 MB, medium of a high-density recording of 540 MB or 640 MB has also been being presented in recent years. In the MO cartridge which is used in an optical disk drive, a ZCAV recording (zone constant angular velocity recording) in which a medium track is divided into zones and the number of sectors is set to be equal every zone is used. The medium of 128 MB uses the recording method of a pit position modulation (PPM). It is sufficient that the light emitting power changes at three stages of a reading power, an erasing power, and a recording power. On the other hand, the media of 230 MB, 540 MB, and 640 MB use the recording method of a pulse width modulation (PWM) in order to raise a recording density. In the PWM recording, it is necessary to change the light emitting power at four stages of the reading power, the erasing power, a first writing power, and a second writing power. In the PWM recording of a medium of a direct overwrite corresponding type which doesn't need the erasing operation, it is necessary to change the light emitting power at four stages of the reading power, an assisting power, the first writing power, and the second writing power.
However, in the recording medium of a high density such as 540 MB or 640 MB in which the PWM recording is performed, a margin of an optimum writing power of a laser diode which is used for medium recording is narrow. When a temperature of the medium changes, the optimum writing power changes. The optimum writing power also changes depending on manufacturing conditions of the medium or a difference of writing performance of the optical disk drive. That is, in case of recording by a predetermined writing power which was unconditionally determined at a designing stage, the writing power largely deviates from the actual optimum writing power and a case where the recording operation cannot be executed occurs, so that there is a problem that writing and reading performance deteriorates.